U.S. Pat. No. Des. 261,380 to Amarger discloses a tire tread having five circumferential zig-zag ribs separated by four grooves. A plurality of transversely-extending basically Z-shaped sipes are provided in each of the ribs and while they do not intersect the grooves, they do not appear to be centrally located within each of the one-half pitches. The void areas of the grooves, if they change at all, do not appear to change in the manner of the present invention.
U.S. Pat. No. Des. 253,642 to Amarger, again discloses a tire tread having five circumferentially extending zig-zag ribs separated by four intermediate grooves. This tread pattern appears to utilize a change in groove areas in both the circumferential and transverse directions.
U.S. Pat. No. Des. 262,281 to Candiliotis discloses a pneumatic tire tread having five circumferentially-extending zig-zag ribs separated by four adjacent grooves. The grooves do not appear to have alternately-sized portions and the sipes do not appear to be centrally located.
U.S. Pat. No. Des. 251,187 to Mirtain, et al, discloses a tire tread having four ribs and three grooves wherein there does not appear to be a change in groove areas in both the circumferential and transverse directions.
U.S. Pat. No. Des. 208,132 to Wittenmyer discloses a tire tread having five circumferential ribs separated by four intermediate grooves wherein the pitch of the grooves alternates and the size of the grooves appears to change with the changing pitch, however, the groove pitches do not alternate in a lateral direction.
U.S. Pat. No. Des. 222,322 to Pope discloses a pneumatic tire tread having seven ribs and six grooves wherein the angled portions of the grooves appear to be narrower than the relatively straight circumferential portions.
U.S. Pat. No. Des. 220,739 to Bartlett discloses a tire tread having five circumferential ribs and four zig-zag grooves wherein circumferentially alternating pitch portions of the grooves appear to be of a continuously-changing dimension.